| Enhancements to scheme to achieve current best practice sustainability |
| Ìý | element cost £ | cost/m2 gifa £ | % of total cost |
| Substructure | 745,400 | 104.99 | 7.56 |
| ADD additional foundation and ground slab costs arising from increased footprint associated with two-storey design; pad foundations; 200 mm thick ground slab; below ground drainage. 2300 m2 @ £180 |
| Base building substructure costs based on footprint area of 1636m2. |
| Extra over 200 mm thick ground floor slab for incorporation of recycled aggregates in concrete 1000 m3 @ £15 |
| Below ground drainage pipes and fittings in clay in lieu of PVC 2300 m2 @ 0 |
| Reduced use of potentially toxic materials at no overall increase in cost |
| Frame, upper floors and stairs | 849,500 | 119.65 | 8.62 |
| OMIT six-storey insitu concrete frame; upper floors and roof; insitu concrete shear walls 7100 m2 @ (£170) |
| ADD two-storey steel frame; universal columns and beams @ 50kg/m2; standard proprietary hollowcore precast concrete floor and roof deck units; finishes to steelwork – no fire protection required 7100 m2 @ £120 |
| Embodied energy and transport benefits from utilising partially recycled steel and reduced cement volume; reduced building mass through use of hollow core units in lieu of insitu concrete; reduced waste due to off-site fabrication of steel and precast units; exposed thermal mass using PC units; reduced use of toxic materials as no fire protection required to steel due to adoption of fire-engineering-based design. |
| Roof | 1,076,600 | 151.63 | 10.92% |
| OMIT bespoke glazed rooflight over atrium to six-storey building 80 m2 @ (£750) |
| OMIT flat roof finishes to six-storey building; felt roof membrane on metal decking and insulation 1465 m2 @ (£116) |
| ADD northlight roof to two-storey building; secondary steelwork; standing seam mill finish aluminium; 175 mm zero ODP insulation to achieve good practice U-value 4465 m2 @ £80 |
| Roof profile designed to increase natural daylighting. Operational lighting costs and lighting heat load will reduce as system is specified in conjunction with a lighting control system. Increased roof area due to replanning of building based on two storeys, and northlight profile. Actual roof area stated rather than plan area. |
| Extra over for roof installation for fan assisted ventilation shafts; refer to building services for costs of fans 42 @ £3250 |
| Fan-assisted natural ventilation provided to supplement natural cross ventilation |
| ADD increased drainage requirements for increased area of roof for a two-storey building; siphonic drainage, gutters, outlets, pipework. 2935 m2 @ 12 |
| ADD increased area of glazed rooflights; thermally broken patent glazing ; sealed double-glazed units 635 m2 @ £340 |
| Increased natural daylighting to 100% of office space to BS8206. Operational lighting costs and lighting heat load will reduce as system is specified in conjunction with a lighting control system |
| Extra over for Argon filled cavity to rooflights; U-value = 1.4 W/m2K 635 m2 @ £30 |
| Management of potentially increased heating and cooling loads resulting from increased U-value and improved thermal performance of rooflights |
| Extra over for opening vents to rooflights to assist natural ventilation; tilt and turn vents; actuator motors; refer to special installations for controls 84 @ £800 |
| Reduced carbon emissions, running costs and plant replacement costs resulting from simplification of mechanical installation |
| ADD solar shading to rooflights; externally mounted, proprietary aluminium louvres 635 m2 @ £150 |
| Management of increased solar heat load and glare resulting from increased area of roof lights |
| ADD for automated solar control blinds to rooflights; including interface with controls 635 m2 °ªÂ£70 |
| Management of increased solar heat load and glare resulting from increased area of rooflights |
| Extra for enhanced insulation thickness to roof to meet best practice U-values (overall thickness 200 mm); U-value = 0.18 W/m2K 4465 m2 @ £1.10 |
| Extra over for insulation for achieving best practice U-value with 200 mm injected cellulose insulation (Warmcell 500) 4465 m2 @ £0.25 |
| Extra for achieving same U-value with natural sheep’s wool insulation. 4465 m2 @ £8.15 |
| Renewable source of materials | Ìý | Ìý | Ìý |
| Stairs | 224,000 | 31.55 | 2.27 |
| ADD balustrading to first-floor voids 300 m @ £450 | Ìý | Ìý |
| OMIT reduced number of stairflights for two-storey building 24 (£2200) |
| External walls, windows and doors | 1,976,000 | 278.31 | 20.05% |
| OMIT aluminium stick and panel curtain walling system; sealed double glazed units; to all elevations 2600 m2 @ (£335) |
| OMIT aluminium rainscreen cladding; blockwork backing; to roof level enclosed plant rooms and escape stairs 700 m2 @ (£250) |
| OMIT solar shading; south elevation only 790 m2 @ (£525) |
| OMIT internal atrium glazing from base scheme 545 m2 @ (£300) |
| ADD cavity wall construction to two-storey scheme; outer leaf of facing bricks; inner leaf of 140 mm dense concrete blockwork; zero ODP insulation; wind posts. Including allowance for high proportion of additional labours. 1685 m2 @ £300 |
| Ìý | Ìý | Ìý | Ìý |
| Reduced solar heat gain from solid wall; embodied energy and toxicity from use of masonry materials. Brickwork and blockwork are A-rated materials in the Green Guide to Specification. Use of locally sourced materials also reduce embodied energy associated with transportation. |
| Extra over for lime mortar 1685 m2 @ £4 | Ìý | Ìý | Ìý |
| Facilitates recycling of brickwork at end of building life | Ìý | Ìý | Ìý |
| Extra over for sheep’s wool insulation to meet best practice U-value; U-value = 0.25W/m2 C. 1685 m2 @ £9.50 |
| Ìý | Ìý | Ìý | Ìý |
| Renewable materials source | Ìý | Ìý | Ìý |
| ADD high performance aluminium stick system curtain walling to external wall and lightwell elevations 1560 m2 @ £350 |
| Rate reflects high performance specification with U-value of 0.25 W/m2K and airtightness rating of <7m2/hr/m2 |
| Extra over curtain walling for manually openable windows 60 @ £320 | Ìý | Ìý |
| Provision of responsive workspace through user control of daytime ventilation |
| Extra over curtain walling for top hung windows; for nightime cooling; electrically actuated; refer to special installations for controls. 56 @ £650 |
| Reduced carbon emissions, running costs and plant replacement costs resulting from nightime cooling and simplification of mechanical installation |
| ADD tilt-before-turn inward opening framed vents with insulated panels; electrically actuated; refer to special installations for controls. 525 m2 @ £500 |
| Reduced carbon emissions, running costs and plant replacement costs resulting from simplification of mechanical installation |
| ADD external solar shading to curtain walling; externally mounted, proprietary aluminium louvres 810 m2 @ £250 |
| Enhanced management of solar heat load and glare | Ìý | Ìý | Ìý |
| ADD overhanging roof canopy to south elevation. 510 m2 @ £400 | Ìý |
| Enhanced management of solar heat load and glare | Ìý | Ìý | Ìý |
| Internal partitions | 131,500 | 18.52 | 1.33 |
| Internal doors | 64,500 | 9.08 | 0.65% |
| OMIT reduced number of lift lobby doors in two-storey scheme. 6 @ (£2000) |
| Ditto for reduction in riser doors. 8 @ (£1250) | Ìý | Ìý | Ìý |
| Wall finishes | 120,400 | 16.96 | 1.22% |
| ADD lightweight plaster to inside face of masonry walls; emulsion paint. 1685 m2 @ £15 |
| OMIT plaster and paint finishes to concrete core. 1180 m2 @ (15) |
| OMIT paint finish to concrete columns. 150 m2 @ (£30) | Ìý | Ìý | Ìý |
| Cost effect of VOC-free water-borne paints 1685 m2 @ 0 | Ìý | Ìý | Ìý |
| Minimisation of the use of potentially toxic products | Ìý | Ìý | Ìý |
| Floor finishes | 357,700 | 50.38 | 3.63 |
| OMIT adaptation of raised floor for underfloor displacement ventilation; sealing of raised floor plenum; cutting holes for diffusers; bridging over ductwork. 6000 m2 @ (£25) |
| Ceiling finishes | 230,500 | 32.46 | 2.34% |
| OMIT mineral fibre suspended ceiling to office areas. 6000 m2 @ (£18) |
| OMIT allowance for plasterboard margin to office and atrium perimeter. 6000 m2 @ (£11) |
| ADD self finished acoustic plaster to soffits of upper floors and sloping roof deck of northlights. 7100 m2 @ £25 |
| Furniture and fittings | 147,500 | 20.77 | 1.50% |
| Sanitary appliances | 59,500 | 8.38 | 0.60% |
| ADD waterless urinals. Item @ 3,500 | Ìý | Ìý | Ìý |
| Additional costs of waterless urinals mostly offset by savings in simplified plumbing installation |
| ADD spray taps and dual flush WCs. 7100 m2 @ £0.50 | Ìý | Ìý | Ìý |
| Reduction in water consumption by 50% if all three measures are implemented. |
| ADD PIR control to taps. 7100 m2 @ £1.50 | Ìý | Ìý | Ìý |
| Water and disposal installations | 174,400 | 24.56 | 1.77% |
| Extra over for PVC-free materials in water and disposal distribution. 7100 m2 @ £1 |
| Minimisation of the use of potentially toxic products | Ìý | Ìý | Ìý |
| ADD additional cost of water and waste distribution pipework to more dispersed toilet provision. 7100 m2 @ £3 |
| ADD solar thermal water heating installation for pre-heat of hot water in toilet cores. 25 m2 @ £1500 |
| CO2 saving of 10 tonnes pa; 25-year payback | Ìý | Ìý | Ìý |
| Heat source, space heating and ventilation | 414,800 | 58.42 | 4.21 |
| OMIT reduced capacity of boiler installation (250kW); ultra low NOX 25ppm condenser boilers. 250 kW @ (£40) |
| Saving related to omission of AHU heater battery | Ìý | Ìý | Ìý |
| OMIT mechanical displacement ventilation system including AHUs, chiller, pipework and ductwork distribution. 7100 m2 @ (£60) |
| Plant rooms and riser provision retained to allow for future retrofit | Ìý | Ìý |
| ADD extract fans; to ventilation shafts; power wiring and controls. 42 @ £675 |
| Fan-assisted natural ventilation provided to supplement natural cross ventilation |
| ADD increased length of LTHW perimeter heating installation. 6000 m2 @ £2 |
| Electrical installation | 646,000 | 90.99 | 6.55% |
| OMIT electrical services cabling and containment to mechanical ventilation and cooling plant. |
| 7100 m2 @ (£2) | Ìý | Ìý | Ìý |
| ADD PVC-free materials in electric wiring and conduit; LSF sheathing to cable. 7100 m2 @ £1 |
| Minimisation of the use of potentially toxic products | Ìý | Ìý | Ìý |
| ADD additional power supplies to actuator controlled facade and roof openings. 6000 m2 @ £6 |
| OMIT basic recessed lighting installation to suspended ceiling (1 fitting per 4.5 m2). |
| 6000 m2 @ (£32.50) | Ìý | Ìý | Ìý |
| ADD exposed up/downlighter lighting installation (one fitting per 4 m2) excluding any attached acoustic treatment. 6000 m2 @ £45 |
| Extra for slimline lighting control boxes located in floor void and allowance for exposed containment systems. 6000 m2 @ £5 |
| Gas installation | 17,900 | 2.52 | 0.18 |
| Lift installations | 40,000 | 5.63 | 0.41 |
| OMIT two passenger lifts serving six storeys. 2 @ (£73,000) | Ìý | Ìý |
| ADD one passenger lifts serving two storeys. 1 @ £40,000 | Ìý | Ìý |
| Protective installation | nil | nil | nil |
| OMIT dry riser serving six storeys. Item @ (£12,600) | Ìý | Ìý | Ìý |
| Communication installations | 107,800 | 15.18 | 1.09 |
| Special installations | 184,200 | 25.94 | 1.87 |
| OMIT BMS controls associated with mechanical ventilation and cooling system. 50pts @ (£650) |
| ADD BMS controlled ventilation path and increased control to roof/vent openings to facilitate night-time cooling. 6000 m2 @ £15 |
| Builder’s work in connection | 68,000 | 9.58 | 0.69 |
| External works and services | 744,600 | 104.87 | 7.55 |
| ADD higher proportion of soft landscaping and tree planting to external works areas and internal courtyards. 9050 m2 @ £8 |
| Additional planting to enhance biodiversity | Ìý | Ìý | Ìý |
| Preliminaries and contingencies | 1,475,000 | 207.75 | 14.97 |
| Contractor’s overheads, site establishment and site supervision; including waste management; pollution control and protection of water courses. Allow 12%. Item @ £1,006,000 |
| Preliminaries provision includes recycling of waste, controls on materials disposal, rainwater and grey water recycling; vehicle sharing etc. There is typically no financial effect on competitively tendered projects with a value in excess of £10m |
| Allowance for waste segregation and recycling schemes. Item @ no extra cost |
| Recycling can produce cost savings on projects where volumes are large enough and where minimisation of active waste disposal is achieved |
| Contingency sum. Allow 5%. Item @ £469,000 |
| Ìý | Ìý | Ìý | Ìý |
| Construction cost including current best-practice sustainability | 9,855,800 | 1,388.12 | 100 |
| Additional costs of current best-practice sustainability | 951,800 | 134.04 | 10.69 |
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